Page 902 - Veterinary Immunology, 10th Edition

macrophages accumulate around the blood vessels of the omentum
VetBooks.ir and serosa (Fig. 27.9). These macrophages are activated in that they

are strongly positive for CD18 and produce TNF-α and IL-1β.
Endothelial cells upregulate MHC class II expression. These

antibodies also generate immune-complexes that are deposited in
the serosa, causing pleuritis or peritonitis, and in glomeruli, leading
to glomerulonephritis. The serosal vasculitis is responsible for the
effusion of fibrin-rich fluid into the serosal cavities. This massive

production of immune-complexes may also be responsible for the
disseminated intravascular coagulation seen in these cats. IL-1 and
IL-6 are found in unusually high concentrations in the peritoneal
fluid from cats with effusive FIP. Cats with preexisting high levels

of antibodies against FECV develop effusive FIP rapidly on
challenge. Administering antiserum to FECV before FIP challenge
may also enhance the peritonitis. It has been suggested that FECV-
infected cats do not develop FIP since they avoid excessive

macrophage activation by upregulating IL-10.

FIG. 27.9 Granulomatous vasculitis of serosal blood vessels in a
cat with feline infectious peritonitis. Note the marked cellular
infiltration of the vessel adventitia and media. This lesion may be
due to the deposition of virus-antibody complexes in the vessel
walls. (Courtesy Dr. R.C. Weiss.)

A modified live intranasal vaccine is available against FIP. The
vaccine contains a temperature-sensitive mutant virus that
replicates in the upper respiratory tract and induces a local IgA

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